17.2.2 Replication Relay and Status Logs

During replication, a slave server creates several logs that hold
the binary log events relayed from the master to the slave, and to
record information about the current status and location within
the relay log. There are three types of logs used in the process,
listed here:

The relay log consists of the events read
from the binary log of the master and written by the slave I/O
thread. Events in the relay log are executed on the slave as
part of the SQL thread.

The master info log
contains status and current configuration information for the
slave's connection to the master. This log holds
information on the master host name, login credentials, and
coordinates indicating how far the slave has read from the
master's binary log.

The relay log info log
holds status information about the execution point within the
slave's relay log.